title: Nonconjugated anionic polyelectrolyte as an interfacial layer for the organic optoelectronic devices.
abstract: A nonconjugated anionic polyelectrolyte, poly(sodium 4-styrenesulfonate) (PSS-Na), was applied to the optoelectronic devices as an interfacial layer (IFL) at the semiconducting layer/cathode interface. The ultraviolet photoelectron spectroscopy and the Kelvin probe microscopy studies support the formation of a favorable interface dipole at the organic/cathode interface. For polymer light-emitting diodes (PLEDs), the maximum luminance efficiency (LEmax) and the turn-on voltage (Von) of the device with a layer of PSS-Na spin-coated from the concentration of 0.5 mg/mL were 3.00 cd/A and 5.5 V, which are dramatically improved than those of the device without an IFL (LEmax = 0.316 cd/A, Von = 9.5 V). This suggests that the PSS-Na film at the emissive layer/cathode interface improves the electron injection ability. As for polymer solar cells (PSCs), the power conversion efficiency (PCE) of the device with a layer of PSS-Na spin-coated from the concentration of 0.5 mg/mL was 2.83%, which is a 16% increase compared to that of the PSC without PSS-Na. The PCE improvement is mainly due to the enhancement of the short-circuit current (12% increase). The results support that the electron collection and transporting increase by the introduction of the PSS-Na film at the photoactive layer/cathode interface. The improvement of the efficiency of the PLED and PSC is due to the reduction of the Schottky barrier by the formation of a favorable interface as well as the better Ohmic contact at the cathode interface.
authors.affiliation: Department of Polymer Engineering, Pukyong National University, Busan 608-739, Korea.
authors.forename: Gyeong Eun
authors.initials: GE
authors.lastname: Lim
authors.forename: Ye Eun
authors.initials: YE
authors.lastname: Ha
authors.forename: Mi Young
authors.initials: MY
authors.lastname: Jo
authors.forename: Juyun
authors.initials: J
authors.lastname: Park
authors.forename: Yong-Cheol
authors.initials: YC
authors.lastname: Kang
authors.forename: Joo Hyun
authors.initials: JH
authors.lastname: Kim